In communication systems such as automobile tire information communication devices that use weak radio waves, a mounting position and a mounting method of a receiving antenna and a radio signal demodulating circuit are devised in order to maintain a good receiving sensitivity at low costs. In a patent publication No. 1, there is described an invention that makes a receiving antenna, a radio signal demodulating circuit and a vehicle wheel speed sensor into an integral structure in a tire information communication device, thereby realizing a good receiving sensitivity at low costs.
That is, according to the patent publication No. 1, the vehicle wheel speed sensor is installed near a rotation center of a tire. Then, the receiving antenna and the vehicle wheel speed sensor are made into the integral structure. Thus, even if a transmitting unit is rotated by a rotation of the tire, the sensor can get a stable receiving sensitivity by keeping generally a constant distance to the transmitting unit.
Moreover, while the radio signal demodulating circuit is provided at a vehicle body side, it is provided inside a housing of the vehicle wheel speed sensor. Accordingly, it is possible to eliminate a coaxial cable connecting the demodulating circuit and the receiving antenna, thereby reducing costs by that much. Furthermore, there is no need if extra parts for mounting the receiving antenna and the radio signal demodulating circuit
Patent Application Ser. No. 1: Pat. Appln. 2003-283537